1. Field of the Invention
This invention relates to a pedal device, primarily for use in operating a vehicle brake by means of an electrically responsive remote actuator, and of the type in which pivotal movement of a pedal causes an electrical output device, such as a potentiometer, to produce an electrical output for transmission to the actuator.
2. Description of the Prior Art
During operation of a conventional vehicle hydraulic braking system, the force applied to the brake pedal is transmitted directly by the hydraulic system fluid to the brake actuators and thus determines the applied braking effort. The pedal effort required from the operator therefore varies in proportion to the degree of braking required and can normally be sensed satisfactorily from the "feel" of the pedal. Pedal movement, once the fixed brake clearances have been taken up, is small and is governed by the compression and expansion of individual brake components. Ideally, the pedal should be truly progressive in movement and load, allowing pedal loads to vary exponentially with the degree of pedal movement, and yet have an output which is proportional to pedal load. Typically, this ideal pedal will produce perhaps 50% of the maximum braking effort over perhaps 75% of its range of movement, giving good sensitivity and feel over the most commonly used braking range, and then providing a progressively harder feel in the lesser used high deceleration/emergency range as full braking effort is reached.
With an electrically operated brake, there is no feed-back from the brake to the pedal and the pedal has to be arranged to have a built-in resistance to operative movement which corresponds as closely as possible to the applied braking effort, while at the same time producing an electrical output from the electrical output device to achieve a desired variation in the braking effort in response to the pedal operative position. These two requirements are difficult to match sufficiently closely to produce a reasonable practical compromise and conventional devices of this type have been found to be less than satisfactory in operation and/or excessively complicated.